What To Know About Myocarditis, a Rare COVID-19 Vaccine Side Effect in Young People

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Michelle Johnson, a cardiologist at Memorial Sloan Kettering Cancer Center — Michelle Johnson, a cardiologist, says heart problems caused by a COVID-19 vaccine are extremely rare. If they do occur, they usually clear up on their own or require medication.

You may have read about heart issues experienced by some people who got the Pfizer-BioNTech COVID-19 vaccine (Comirnaty®), Moderna COVID-19 vaccine (Spikevax™), or Novavax COVID-19 vaccine.

These rare side effects include myocarditis, an inflammation of the middle layer of the heart muscle, and pericarditis, an inflammation of the lining around the heart. People experiencing these conditions report chest pain, shortness of breath, or chest palpitations (feelings of a fast beating, pounding, or fluttering heart).

The Centers for Disease Control and Prevention (CDC) first reported on these side effects in June 2021. The CDC continues to monitor data to better understand when and why these side effects occur.

Michelle Johnson, a cardiologist at Memorial Sloan Kettering Cancer Center, says that these heart issues are very rare, treatable, and not as dangerous as COVID-19 itself.

Young Men Are at Highest Risk — But the Overall Risk Is Very Low

The group that is most likely to develop myocarditis or pericarditis after getting the COVID-19 vaccine is young men aged 12 to 39. These side effects usually showed up after the second dose and within a week of vaccination.

However, the risk for anyone who gets vaccinated is very low.

“Myocarditis or pericarditis after a COVID-19 vaccine is extremely rare after a primary vaccination,” says Dr. Johnson. “It is even more rare after a booster dose.”

There were 1,626 cases of myocarditis among more than 354 million primary doses given between December 2020 and August 2021. This research was published in the journal JAMA on January 25, 2022.
There were 37 cases of myocarditis among more than 81 million booster doses given between September 22, 2021, and February 6, 2022. This research was published by the CDC on February 11, 2022.
There were 6 cases of myocarditis among about 40,000 people in the Novavax clinical trial. This was reported to the CDC on July 19, 2022.

Young men ages 12 to 39 can wait longer between their first and second dose (of their primary vaccine series) to reduce their risk of myocarditis or pericarditis. They should wait 8 weeks between shots.

All other groups should wait 3 weeks (for those who got the Pfizer vaccine) or 4 weeks (for those who got the Moderna vaccine) between primary vaccination doses.

Read about vaccine and booster timing if you have a weakened immune system (because of cancer or another medical condition) »

Treatment for Myocarditis and Pericarditis

If you experience chest pain or a change in your heartbeat, you should call 911.

Most people can be successfully treated for myocarditis or pericarditis by a heart specialist and are able to rest and recover quickly.

“Both conditions will typically clear up on their own or will require medication,” Dr. Johnson says. “In severe cases, a patient may need to be hospitalized for a more aggressive treatment.” This could include any or all of the following:

intravenous drugs
telemetry monitoring (checking electrical activity of the heart for an extended period of time)
monitoring for signs of dysfunction in the way the heart is pumping

COVID-19 Is More Dangerous to the Heart Than Side Effects From the Vaccine

In young people, heart problems are often caused by viral infections such as COVID-19, says Dr. Johnson.

“A young person is much more likely to get myocarditis or pericarditis from COVID-19 itself than they would from a COVID-19 vaccine,” she says.

The COVID-19 vaccines provide strong protection against severe disease, hospitalization, and death from COVID-19. Severe side effects — including myocarditis, pericarditis, anaphylaxis (severe allergic reaction), and thrombosis with thrombocytopenia syndrome (blood clots with low platelets) — are very rare. The CDC continues to monitor these and all potential safety problems.

“We know that the benefits of the vaccine strongly outweigh the risks,” Dr. Johnson says. “I strongly recommend — and the CDC recommends — that everyone who is eligible get vaccinated and get their booster shots.”

July 25, 2022